ABSTRACT Focal cortical dysplasia (FCD) is the most common underlying pathology in children with drug resistant epilepsies. DEPDC5 mutations have been increasingly recognized as the most important genetic cause in focal epilepsies with or without FCD. Using focal somatic mutagenesis approaches, we recently generated a rodent model with pathological and electrographic signatures that are highly clinically-relevant to human FCD. However, precisely how dysplastic cortex and seizures arise from Depdc5 mutation remains unknown. We propose to focus on defining the underlying genetic, cellular and circuitry mechanisms contributing to DEPDC5-related epilepsies as well as establishing the critical roles of DEPDC5 in cortical development. We will provide conceptual insights broadly relevant to understanding mTOR-related malformation of cortical development and epilepsies. Our central hypothesis is that DEPDC5 mutations in cortical progenitors generate focal intrinsic epileptogenecity through its critical roles in sculpting neural and glial development, and that inhibition of mTORC1 recruitment will restore cytoarchitectures and suppress seizures.